[HTC Butterfly] Phil_123:
I have successfully downgraded my J Butterfly based on those instructions. I have simplified it because the original instructions seems to be overly complicated. It involved tricking a system app with root privileges to run an custom command, only to use run_root_shell later anyway.

I also did not use the run_root_shell supplied by the guide, instead I compiled a newer version direct from the source: https://github.com/android-rooting-tools/android_run_root_shell

You'll need

1. revone.dna-0.2.1

http://xdaforums.com/showthread.php?t=2314582

2. A newer build of run_root_shell (attached)

3. 1.15 ROM: PL99IMG_DLX_WLJ_JB_45_KDDI_JP_1.15.970.1_R_Radio_1.00.10.1127_3_NV_2.28_01C_release_signed.zip

(renamed to rom.zip in this tutorial)

https://mega.co.nz/#!jQtQ0BLS!279lf8k4sbKPTmWHTsPg6hbaGDatpq3xGGv4aE8N1h4

4. firmware.zip extracted from OTA_DLX_WLJ_JB_45_KDDI_JP_1.36.970.1-1.29.970.1_release_330380g3nfgypcfojku8a9.zip:

http://kie.nu/1urK

5. adb and fastboot

6. An HEX editor such as XVI32

THIS WILL WIPE YOUR USER DATA, BACKUP ALL YOUR STUFF FIRST

Steps:

1. Run the following commands in command prompt to push files required by run_root_shell to device:

adb push run_root_shell /data/local/tmp/

adb push device.db /data/local/tmp/

2. Run in command prompt:

adb shell

to access the shell on your device. Run the following commands to run run_root_shell, disregard messages about HTL21 not supported. You will be returned to the command line but with a hash (#) instead of a dollar sign, that means you have temprooted.

cd /data/local/tmp/

chmod 755 *

./run_root_shell

3. Run these commands on device shell:

chmod 666 /dev/msm_acdb

dd if=/dev/block/mmcblk0p21 of=/sdcard/p21

4. Run in another command prompt:

adb pull /sdcard/p21

to pull the file p21 from device, then open it with an HEX editor. Refer to the images on the original Japanese tutorial, change the version number near "ClearAutoImage" to 1.00.000.0 and save the file as p21mod.

5. Push the modified file back to the device by running in command prompt:

adb push p21mod /sdcard/p21mod

6. Back to the device shell, run these commands to write the modifications to the device and reboot into bootloader.

dd if=/sdcard/p21mod of=/dev/block/mmcblk0p21

reboot bootloader

7. Run in command prompt:

fastboot oem rebootRUU

to boot to RUU.

8. Run in command prompt:

fastboot flash zip firmware.zip

and it willl fail with this error: "FAILED (remote: 90 hboot pre-update! please flush image again immediately)"

9. Run in command prompt:

fastboot flash zip rom.zip

to flash 1.15 ROM. It should take around 6 minutes. This wipes your user data.

10. In command prompt, push run_root_shell to device again. Also push revone.dna-0.2.1 to device.

adb push run_root_shell /data/local/tmp/

adb push device.db /data/local/tmp/

adb push revone.dna-0.2.1 /data/local/tmp/revone.dna

11. Refer to step 2 to temproot again.

12. Run revone.dna on device shell:

./revone.dna -P

and you should see "revone successful - please reboot to continue".

13. Reboot and repeat step 12 again, this time you should see "revone successful - no need to reboot".

14. Run on device shell:

./revone.dna -s 0 -u

and you should see "revone successful".

15. ???

16. PROFIT!

You have now successfully S-OFFed and may proceed to unlocking and SuperCIDing your device as usual.